1. Technical Field
This invention relates to tunneling thermometry, and more particularly, to electronic thermometry in a tunable tunnel junction.
2. Related Art
Advanced optical methods for thermal measurements may rely on spectroscopy of infrared photons which may provide a resolution on the order of 1 micrometer. Therefore, today, many nano- and microscale temperature measurements are carried out using point-contact techniques, broadly termed Scanning Thermal Microscopy (SThM). SThM measurements rely on miniaturized thermocouples or resistive thermometers. Such measurements are typically carried out by bringing a thermal probe into a good mechanical contact and good thermal contact with a sample of interest. The temperature may be deduced from an electronic response of the thermal probe that is in turn calibrated against a known standard. Raster-scanning the probe across the surface of a heated sample material may enable mapping of local temperature variations with a resolution of approximately 50 nm.
Scanning thermal microscopy may operate with a large number of unknowns, for example, thermal resistance of the contact, temperature gradient in the junction, cooling or heating of the probed object, and the electronic and mechanical perturbation of the probed object. Thus, the measurements usually require a rigorous calibration. However, in these cases, the probe may not equilibrate with the measured object thermally while the thermal resistance itself may be dependent on measurement conditions and minute variations of a largely uncontrollable probe shape, for example, with regard to contact area and geometry. Moreover, parasitic heat loss may significantly reduce the sensitivity of the contact methods. Most of these issues are fundamental to the contact geometry, and may not be resolved by simply improving the measurement set-up or the measurement environment.